Salvage yards are a place to look for a 4x4 switch. Be sure to match the connector, though because it changed around 1989.
Also, give Hawk's Strictly Suzuki (888 SAMURAI) a call if you can't find one locally.
Finally, if it is the dash bulb that needs replacing, you can find one at an auto parts store. They are not special. Getting the dash gage cluster out is a bit tricky. You have to loosen (not remove!) the two Torx bolts that hold the steeing column in place in order to lower the steering column enough for the cluster to clear the Emergency flasher "button".
I hope that this helps!